Tornadoes in the U.S.: More than a regional concern

Tornadoes have been reported in all 50 states. Here's what insurance professionals can expect going forward.

Tornadoes have been linked with devastating losses, and not just to a specific part of the U.S. (Credit: Ernest Prim/Adobe Stock)

This year’s weather news has included various headlines about tornado sightings and subsequent losses caused by twisters that touched down around the United States.

Insurance professionals can expect to see more tornado-related claims come from different areas of the country along with significant structural damages from these events.

Events outside of “Tornado Alley”

Even places where tornadoes aren’t common often see a couple each year. (Credit: Donan)

The notion of Tornado Alley as a designated area for tornadoes is misleading, according to the National Oceanic Atmospheric Administration National Severe Storms Laboratory. Tornadoes have been reported in all 50 states. The central plains region is often referred to as Tornado Alley because of the prevalence of these catastrophic events where the cold, dry air from the north meets warm, moist air from the Gulf Coast. Tornadoes are common in the area during the spring and summer months. However, the threat of tornadoes still exists in the Southeast, the southern and central plains, and the northern Plains and Midwest.

The study Spatial Trends in United States Tornado Frequency also evaluated whether tornadoes are occurring more often. Findings included a decrease in tornadoes in Tornado Alley and an increase in the Southeast area, coined Dixie Alley. This analysis and others like it noted upward trends in the frequency of tornadoes in the Southeast, Midwest and Northeast.

More than 1,300 tornadoes occurred in 2022, with the most being recorded in Mississippi, Texas and Alabama, according to the Insurance Information Institute. Regardless of how many tornadoes occur annually or where, residential losses from even just one can be substantial.

How tornado strength factors into claim damages

Tornadoes are violently rotating columns of air usually associated with thunderstorms. Much like the Saffir-Simpson Scale does for hurricanes, the Enhanced Fujita (EF) Scale assigns tornado ratings from EF0 to EF5 based on wind speeds and degrees of damage. More than half of all tornadoes are EF0 with wind speeds between 65 to 85 miles per hour. Least likely are EF5 tornadoes with wind speeds of more than 200 mph.

Lower windspeeds can still cause visible damage, and it’s likely to start on the roof. (Credit: Donan)

The EF Scale uses a list of 28 Damage Indicators. The Damage Indicators cover many types of buildings (e.g., residential houses, schools, shopping malls, etc.) and other objects (e.g., cell towers, trees, etc.) that might be damaged by a tornado. Each Damage Indicator has a table of Degrees of Damage that are used to rate the damage to that particular Indicator and estimate the wind speeds.

Degrees of Tornado Damage to homes include:

When evaluating how to settle claims for tornado-related damages, it’s important to remember there are other aspects than just wind speed to consider.

Factors that impact the scope of damage

Wind typically impacts a structure from the top down and from the outside in. The strongest wind loads are applied to the roof and move down to the foundation. Damage is expected to outer walls before interior walls. Adjusters may see claims for total destruction when the structure can no longer resist the applied loads.

A forensic engineer’s evaluation should be able to determine if the following factors impacted the structure’s ability to withstand the wind.

Tornadoes are rated based on the most severe damage along a tornado’s path. A tornado may be rated EF4, but at some points along the path, the intensity is often lower. The National Weather Service typically performs field surveys after tornadoes, not only determining their maximum intensity but also the storm path, width, and varying intensity along the path. Knowing the estimated intensity at a particular location is important in correlating the observed damage to the storm.

Also, objective evaluations confirm if cause of loss is related to the tornado. Buildings next to one that sustained substantial damage may remain unscathed or have a loss from something else. On the other hand, buildings farther from the tornado’s path may have impacts from wind or flying debris.

When handling tornado-related claims, adjusters should be sure to have the necessary information at their disposal, including weather data, property details and history, and a full structural evaluation, before making a decision. Without it, they could be settling for unnecessary replacements or unknowingly not settling for failures caused by verified tornadoes in unexpected places.

Chris Scallion, P.E., RRC, is the technical engineering manager for Donan, which is part of Alpine Intel. He is responsible for managing the forensic engineering team.

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